A 67-year-old man and his 35-year-old son-in-law were recently admitted to Uttaradit Provincial Hospital. They had developed symptoms similar to those caused by the bird-flu virus after eating spotted doves, said Dr Boonrieng Chuchaisaengrat, head of the provincial health office.

The men were transferred from Tha Pla District Hospital on Friday and detained at the provincial hospital, said Boonrieng.

Blood samples were collected from the two patients and sent for testing at the Northern Medical Science Centre in Pitsanulok. The results were expected in a few days, he added.

Panom Meesiriphan, chief of the province's livestock office, insisted that although there had been suspicious deaths of poultry in many districts, there had been no confirmed case of the H5N1 virus.

Despite declaring seven provinces bird-flu "red zones" the DLD's director-general Yukol Limlamthong said Thailand had not been hit by an outbreak of the virus.

"The red zone means the area has a high risk of becoming an infected area, but it does not mean that it is already infected," said Yukol.

Besides Uttaradit, the other six red-zone provinces are Sukhothai, Pichit, Pitsanulok, Suphanburi, Nakhon Pathom and Kanchanaburi.

When the country recorded the first cases of bird flu between January and May 2004, the DLD used the term "red zone" to define the provinces that were hit by the virus.

The DLD's new definition of "red zone" has confused some medical practitioners. A source at the Disease Control Division said that for some doctors "red zone" meant an infected area. "Medical doctors believe the H5N1 virus has already arrived in Thailand, but no one wants to confirm it," said the source, who asked not to be named.

On Friday a leading virologist from Siriraj Hospital, Professor Prasert Thongcharoen, expressed doubt about the accuracy of official reports on bird flu. He said that in his experience when livestock officials said "no" it meant "yes".